Question

what do you mean by atomic mass?

Answer 1

Atomic Mass : 
Atomic mass of an element is the number of times the atom of the element is heavier than 1/12th of C-12 atom.

Answer 2

atomic mass is the sum of protons and neutrons  present in an element .atomic mass of carbon = 12 u , oxygen = 16 u ...
   i hope that this will help u.......................................^_^